Enable GitHub Actions for unit tests

[anthonysena]

When new branches are pushed to the repo, we should run the maven tests.

[chrisknoll]

Need to look into hooking up gitActions to perform this, and also post codecoverage to codecov.io (if we want badges and such).

About 2 years ago, I did have travis builds (via travis.yml) in circe-be, but something changed (I think it went to subscription based) and I never cut it over to use gitActions. So, part of this work is finding a gitActions script that can invoke the builds and post the codecov.